A variety of implantable medical devices (IMDs) are used for providing medical services (e.g., monitoring and/or delivering therapy) to patients suffering from a variety of conditions. For example, IMDs may monitor one or more physiological parameters of patients to aid in diagnosis or treatment by a clinician. Further, IMDs may deliver electrical stimulation therapy to patients to treat their conditions, for example, urinary or fecal incontinence, sexual dysfunction, or gastroparesis. For example, such IMDs may be used to stimulate a target nerve or muscle to remedy chronic incontinence associated with bladder muscle weakness. These devices are intended to provide a patient with a therapeutic output to alleviate or assist with a variety of conditions. IMDs may also be used to periodically deliver drugs to a patient.
Typically, such devices are implanted in a patient and are powered by rechargeable batteries. The battery of an IMD may be recharged inductively through the skin by an inductive charger. Despite the fact that technology exists to inductively charge a battery outside of a patient within minutes, current IMD recharging techniques require multiple hours to completely recharge the battery of an IMD within a patient. If energy is transferred to the battery too rapidly, inductive charging may generate enough heat to damage the patient's tissue. Thus, other IMDs require that the inductive charger transfer energy to the battery at a slow rate to prevent heating the tissue of the patient to an undesirable temperature. Some IMDs may achieve slightly faster recharge times by throttling the rate of charging to prevent the temperature of the IMD from exceeding a level harmful to the patient. However, these techniques remain cumbersome and time-intensive. Even with dynamic throttling of recharge rates, the patient still is required to remain in place and keep the inductive recharger properly positioned for considerable amounts of time.